Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint and openWorldHint, so the description's added value is the commercial behavior: $0.002 USDC per successful call via x402 on Base, Solana, or Arc, with failed calls not charged. That is exactly the kind of auth/cost context the annotations cannot convey; it stops short of describing pagination or series availability limits.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The purpose and default are front-loaded in the first clause, followed by sibling routing and pricing. The sibling sentences are somewhat padded (each repeats 'when you need ...'), but no sentence is irrelevant.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a two-optional-parameter read tool with an output schema, annotations, and full schema coverage, the description supplies the pieces an agent cannot infer: the default series, the unit (percent), and the payment model. Only minor gaps remain, such as what happens for an unknown mnemonic.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so both parameters are already documented, and the description largely restates them (latest N observations, default mnemonic). It does add the concrete default value FNYR-SOFR-A with its meaning (SOFR rate in percent), which is marginal added value over the schema, so it sits at the baseline rather than above it.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource: retrieves the latest N observations of the OFR Short-term Funding Monitor daily series, for one mnemonic, with the default named (FNYR-SOFR-A, SOFR in percent). This is unambiguous and clearly separable from the named siblings, which cover Hyperliquid perp funding and Nasdaq short interest.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicitly routes the agent elsewhere for two adjacent needs: finance_hyperliquid_perp_funding for perp funding snapshots and finance_nasdaq_short_interest for short interest history. It does not spell out a when-not-to-use condition for this tool itself (e.g. non-OFR series or intraday vs daily), but the routing guidance is concrete.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.